1. Field of the Invention
The present invention relates to an optical device, using a lead frame, on which an optical element such as an image sensor is mounted. The present invention also relates to a process for manufacturing such an optical device.
2. Description of the Related Art
Concerning the optical device on which an optical element such as an image sensor is mounted, there has been proposed, in the prior art, a product, such as that shown in FIG. 5, in which the optical element 12 is mounted on the package body 10, which is formed by resin molding, and the package body 10 is sealed by a light transmitting cap 14. The optical device shown in FIG. 5 is a product in which the light transmitting cap 14, which is formed in such a manner that a light transmitting window 16, composed of a glass sheet and made to adhere to the frame 15 formed by resin molding, is fixed to the package body 10.
The above-mentioned optical device conventionally known in the prior art is manufactured as follows. First, the package body 10 is formed on the lead frame 20 by means of resin molding, in which a metallic mold for resin molding is used. Next, the optical element 12 is made to adhere onto the package body 10, and the optical element 12 and the inner leads 20a of the lead frame 20 are electrically connected with each other by wire bonding. Then, the light transmitting cap 14 is fixed onto the opening of the package body 10. Finally, the outer lead 20b is formed by a trimming and forming process. After that, the individual optical device is separated from the lead frame 20. In this way, an optical device can be obtained.
In the manufacturing process of the above optical device, the package body 10 is sealed when the light transmitting cap 14 is made to adhere onto the opening of the package body 10. Concerning the adhesive used for the adhesion of the light transmitting cap 14, a thermosetting adhesive is conventionally used. In this case, the thermosetting adhesive is conventionally used for the object of ensuring the heat resistance and reliability so that the sealing property of the package cannot be impaired even if heat is given to it in the process of mounting the optical device. Since the thermosetting adhesive is used for the adhesion of the light transmitting cap 14 as described above, the thermosetting adhesive is coated on the package body 10 and the package is heated under the condition the light transmitting cap 14 is attached to the package body 10 so that the thermosetting adhesive is cured by heating the package in the conventional manufacturing process.
In this adhesion process in which the light transmitting cap 14 is made to adhere onto the package body 10, a workpiece is put into a heating furnace and heated at about 100xc2x0 C. for about 1 hour, and then the heating temperature is further raised to 170 to 180xc2x0 C. and kept at this temperature for about 1 hour so that the adhesive can be cured, and then the temperature is gradually lowered to room temperature. This adhesion process requires about half a day. As described above, according to the conventional manufacturing process, the process in which the light transmitting cap 14 is made to adhere onto the package body 10 requires a long period of time. Further, this adhesion process is conducted by batch processing. From the viewpoint of using batch processing, the working efficiency is low.
In addition, when the package is heated in the adhesion of the light transmitting cap 14, gas is emitted from the thermosetting adhesive, which causes the following problems. The light transmitting cap 14 may be raised from the package body 10 by the pressure of gas emitted from the inside of the package body 10. In order to solve the above problems, in the conventional manufacturing process, heating is conducted while the light transmitting cap 14 is being held by a clip jig so that the light transmitting cap 14 cannot be raised from the package body 10 when the light transmitting cap 14 is made to adhere to the package body 10. As described above, according to the conventional manufacturing method, the manufacturing work must be conducted in such a manner that the clip jig for preventing the light transmitting cap 14 from rising is provided, and after the completion of heating, the clip jig must be removed. From this point of view, the working efficiency is lowered.
The present invention has been accomplished to solve the above problems. It is an object of the present invention to provide an optical device, using a lead frame, in which the light transmitting cap can be easily and efficiently fixed to the package body, so that the optical device can be easily mass-produced.
It is another object of the present invention to provide a process for manufacturing such an optical device.
In order to accomplish the above objects, the present invention is provided with the following structure.
According to the present invention, there is provided an optical device comprising: a package consisting of a lead frame and a molded resin integrally molded with the lead frame, the package being provided with a cavity having an opening; an optical element installed in the cavity of the package; a cap defining a light transmission window for closing the opening of the cavity; and an ultraviolet-light-setting type adhesive for fixing the cap to the package so as to close the opening of the cavity.
The optical device further comprises a UV light impermeable, protective film attached to a surface of the cap, facing outside with respect to the cavity, except for an outer peripheral area of the cap, which is exposed from the protective film.
The lead frame comprises a stage exposed on a bottom surface of the cavity and a plurality of leads, each lead having an inner lead exposed on the bottom surface of the cavity and arranged around the stage and an outer lead extending outward from the molded resin of the package; and the optical element is mounted on the stage.
The cavity having the opening is substantially rectangular and the opening is provided with a step along the an inner periphery thereof so that an outer peripheral edge of the cap is engaged with the step.
According to another aspect of the present invention, there is provided a process for manufacturing an optical device comprising the following steps of: preparing a package consisting of a lead frame and a molded resin integrally molded with the lead frame, the package being provided with a cavity having an opening; installing an optical element in the cavity of the package; coating an ultraviolet-light-setting type adhesive along a periphery of the opening of the package; applying a cap for defining a light transmission window to the package so as to close the opening of the cavity; and irradiating ultraviolet-light toward an adhesion area between the cap and the package to solidify the ultraviolet-light-setting type adhesive to fix the cap to the package.
The cap is provided with a UV light impermeable, protective film attached to one surface of the cap and the cap is applied to the package in such a manner that the UV light impermeable, protective film faces the outside of the cavity.
The UV light impermeable, protective film is attached in advance to the one surface of the cap except for an outer peripheral area of the cap, which is exposed from the protective film.
The optical element is installed in the cavity so that the optical element is mounted on the stage; and the optical element is electrically connected to the inner leads, before the cap is applied to the package.